The invention relates to a card for producing fibrous textile webs and random webs of natural or synthetic fibers. The card comprises a series of cylinders clothed with metallic wire which rotate in a predetermined sense with respect to each other. A plurality of working rollers are coordinated with the cylinders for working the fibers. A roller and feed plate feed the fibers and at least one takeoff roller takes off the fibers. The cylinders and the workers are covered by trough-shaped plates.
It has been known to use closed undercasings in cards such as random web cards, under carding cylinders and licker-in roller to prevent accidental air movements and negative influences. Further, dirt deposits on the driving units frequently arranged beneath the rollers are prevented. It also has been known to use interrupted undercasings with slots to remove trash particles, etc., beneath rollers within the licker-in range when the rollers have teeth points inclined in the sense of rotation (positively inclined metallic wire).
With the use of arcuate undercasings which are produced more and more accurately in order to obtain a more uniform final product, the optimum air amount may not be available for the formation of the air current entrained by the roller when operational conditions change, i.e. changes in fiber material,
In the absence of sufficient air, the system absorbs air in an uncontrollable manner. An unequal pressure distribution is caused over the working width from one roller end to the other. A nonuniform fiber distribution is produced accordingly. On the other hand, the presence of too much air may entail a formation of alleys, i.e. streaks and thin places in the material.
Accordingly, an object of the present invention is to provide a card having a regulation and control of the air balance around the rollers.